George Clooney has stepped up his war of words with hotel and casino magnate Steve Wynn, blasting the tycoon's account of their bust up as "false".

The Ocean's Eleven star got into a heated argument with Wynn and stormed out of a Las Vegas restaurant last month, later accusing him of calling U.S. President Barack Obama an "a**hole".

Wynn hit back in an interview on the Bloomberg TV network on Friday, denying he used the slur against the President and branding Clooney "mollycoddled" and "a little into the tequila".

The actor has now responded, releasing a lengthy response to People.com to clear up Wynn's allegations.

He writes, "I will not let his version of the truth go unchallenged. He now says he didn't call the president an 'a******.' That is false. He bellowed 'I voted for the a******,' and then called him the same thing several more times as the dinner came to an abrupt end.

"Again there were eight people at the table, eight witnesses. I did in turn, call him the same body part, and walked out. Again he can make up whatever story he wants, but these are the facts. He said I drank 16 shots of tequila. I didn't drink one shot of tequila, not one. We were drinking but it was early and we still had two events to attend.

"He said I live in a bubble. More of a bubble than Las Vegas? Honestly? He says I'm 'molly coddled,' that I'm surrounded by people who coddle me. I would suggest that Mr. Wynn look to his left and right and find anyone in his sphere that says anything but 'yes' to him...

"Steve is one of the richest men in the world and he should be congratulated for it, but he needs to take off his red sparkly dinner jacket and roll up his sleeves every once in a while and understand what most of the country is actually dealing with... or at least start with the fact that you can't make up stories when eight people who are not on your payroll are sitting around you as witnesses."